1. Field of the Invention
The present invention is directed to a method and apparatus for the application and curing of thermoplastic and thermoset coatings in situ, to a substrate, utilizing laser radiation.
2. Description of the Related Art
Utilizing lasers to heat different materials is a well-known method. For example, laser welding has been used to affix one surface to a second surface. This is accomplished by directing the output of a laser at one end of the joint in which two metal plates meet, and then scanning the laser across the joint to form a visible seam. Through the use of laser radiation, these two surfaces are fused together.
An example of using a laser for such a welding process is described in U.S. Pat. No. 7,766,213 issued to Henrikson. This patent describes a method of welding in which infrared laser radiation is employed. This patent includes a general discussion of monitoring the welding process, wherein the welder is continually illuminated with ultraviolet radiation via several sources, including laser radiation. While several techniques of monitoring the welding process are broadly described, no description is included in Henrikson, reciting a real time closed monitoring system. At best, Henrikson would use a predetermined time/power relationship and not a system in which this relationship is changed based upon the real time observation of the substrates to be welded.
U.S. Pat. Nos. 6,670,574 and 7,129,438 issued to Bates et al., are also directed to systems for utilizing a laser to weld two substrates together. The Bates et al. patents employ a computer-controlled algorithm to compare the weld to a preferred weld in a “library of algorithms”, whereby the laser power and focal length of the laser are then modulated based upon the utilization of one of these algorithms. In this context, a plurality of laser welds is initially performed and the operator would then select the most suitable algorithm for the task at hand to review the sufficiency of the weld. This is accomplished by the operator running a library of algorithms associated with the weld characteristics. Similar to the Henrikson patent, the two Bates et al. patents do not utilize a real time closed system capable of changing various parameters in a real time environment.
U.S. Pat. Nos. 5,200,230 and 5,409,537 issued to Poullos et al. and U.S. Pat. No. 7,661,387 issued to Poullos, describe methods and systems for the application of fluoropolymers and other coating types via a laser in situ. However, none of these patents describe techniques and apparatuses necessary to coat and integrate multiple polymer coated fields into a uniform homogeneous coating layer. Additionally, none of these patents describe a technique to overcome the problem of controlled localized heating and processing, which is required if an entire structure to which a coating is applied cannot be simultaneously heated. Similar to the Henrikson and Bates et al. patents, none of the Poullos patents teach methodologies suitable for real time processing. Furthermore, none of these patents can adequately operate in a manner to accommodate large changes in absorption of radiated power in polymer coating materials, as well as deal with polymers having high melt viscosities.
Furthermore, none of the discussed patents disclose a technique for controlling the scan and power densities of a single laser or plurality of lasers over the entirety of a localized scan field, nor do they teach the appropriate thermal resolution and time response required for effectively coating ultraviolet (UV) curable powder coatings, thermosets, thermoplastics over various and potentially sensitive substrates.
Therefore, it is an object of the present invention is to provide a system and method for coating a substrate in a multi-functional way by changing the coating's intermolecular characteristics through the use of a plurality of lasers in a real time manner during the coating process and thereby increasing quantum yield.
It is a further object to provide a method and apparatus to adjust the power densities of the laser beam or beams used to coat the substrates in a real time manner during the coating process.
It is a further object to provide a method and apparatus employing optical and opto-mechanical devices for achieving the real time monitoring and alteration of the coating process.